The subject of the present invention is a supply circuit for a traveling-wave piezo-electric motor comprising at least one rotor driven by friction, by at least one stator energized by at least two piezo-electric elements linked respectively, on the one hand, to the stator and, on the other hand, to two electrodes supplied respectively with two alternating voltages of like amplitude and phase-shifted by approximately 90.degree. by means of a single alternating supply source and of a means intended for generating the two phase-shifted voltages.
Such a supply circuit is known from French patent 2 721 154, the content of which is incorporated by reference. In this document it is proposed, in order to remedy the drawbacks of the prior supply circuits comprising two supply sources created by independent supply devices, to supply the piezo-electric motor by means of a single high-frequency alternating source and of a means of adaptation connected, on the one hand, to the alternating source and, on the other hand, to the electrodes of the piezo-electric elements so as to generate the two voltages phase-shifted by around 90.degree.. The means of adaptation consists of two quadripoles, one of these quadripoles comprising an inductance and a capacitance and the other quadripole an inductance. If the alternating supply source comprises a transformer whose primary and secondary stages both consist of two windings, the inductances of the quadripoles may be constituted by the transformer's own leakage inductances. It is however necessary to curb these leakages by interposing a gap in such a way as to increase the intrinsic leakage inductance, this requiring the manufacture of special transformers exhibiting greater radiation than standard transformers, and this may necessitate the provision of shielding for the whole of the circuit so as to comply with the normative constraints. Such a solution is therefore relatively heavy and expensive.